Measurement of Cross Sections for Electron Excitation out of the Metastable Levels of Argon

We have measured electron excitation cross sections out of the ${1s}_3$ and ${1s}_5$ metastable levels of Ar into eight levels of the ${3p}^{5}4p$ manifold. We use the optical method to determine the cross sections by measuring the radiation of the excited atoms. By optically pumping the ${1s}_5$ metastable atoms with a laser, we separate the contributions that each metastable level makes to our observed signal, and thus we can determine the excitation cross sections out of the individual metastable levels. We also interpret the trends in both magnitude and energy dependence observed for the cross sections.